1 Chapter 2 The Biological Bases of Psychological Functioning Outline I. Neurons: The Building Blocks of the Nervous System A. A neuron is a nerve cell that transmits information from one part of the body to another via neural impulses. B. There are approximately 100 billion neurons in the human brain. II. The Structure of Neurons A. No two neurons are exactly alike, but they have structures in common. B. The cell body contains the cell s nucleus. C. Dendrites, tentacle-like structures, receive neural impulses from neurons. D. An axon is a long tail-like extension of a neuron that carries impulses away from the cell body to other cells. 1. About half of all axons contain myelin, which is a white substance made up of fat and protein, that insulates and protects them and speeds impulses along. 2. Myelin tends to be found on axons that carry impulses relatively long distances. 3. A loss of myelin is the cause of multiple sclerosis a neurological disorder affecting nearly 10 of every 10,000 young adults a 50% higher rate than 25 years ago. 4. Axon terminals are where axons end in a branching series of bare end points and communicate with adjacent neurons. E. In most cases, dead neurons are not replaced with new ones. 1. Functions of lost neurons can be taken over by surviving neurons. 2. New research suggests that the growth of new neurons occurs in the adult human brain a process called neurogenesis although at nowhere near the rate of growth observed before and right after birth. III. The Function of Neurons A. The function of a neuron is to transmit neural impulses from one place in the nervous system to another. B. A neural impulse is a rapid and reversible change in the electrical charges inside and outside a neuron. C. Chemical ions are particles that carry a small, measurable electrical charge that is either positive or negative. 1. When it is at rest, there are more negative ions than positive ions inside the axon.
2 2. Electrical tension results from the attraction between the negative ions and positive ions. a. This tension is called the resting potential. b. The resting potential of a neuron is about -70mV. c. At rest the neuron is said to be in a polarized state. d. The resting potential is released when a neuron is stimulated to fire. 3. When it is stimulated, the polarity of the nerve cell changes and the process is called depolarization. a. The action potential is the short-lived electrical burst caused by the sudden reversal of electric charges inside and outside a neuron in which the inside becomes positive (about +40 mv). b. The neuron becomes hyperpolarized during the refractory period and cannot fire a refractory period. c. Eventually, the membrane returns to normal restoring the normal distribution of ions across the cell membrane. D. A neuron either fires or it does not an observation called the all-or-none principle. E. The neural threshold is the minimum amount of stimulation needed to fire a neuron. IV. From One Neuron to Another: The Synapse A. The synapse is where one neuron communicates with other cells. B. The synaptic cleft is the space between a neuron and the next cell at a synapse. V. Synaptic Transmission A. Vesicles are small containers concentrated in a neuron s axon terminals that hold neurotransmitter molecules. B. Neurotransmitters are chemical molecules released at the synapse that, in general, will either excite or inhibit a reaction in the cell on the other side of the synapse. C. Receptor sites are places on a neuron where neurotransmitters can be received. 1. It is the interaction of neurotransmitter and receptor site that causes inhibition or excitation. 2. Once released form their receptor sites, neurotransmitter are either destroyed by enzymes, or taken back up into the neuron from which they came, a process called reuptake. VI. Neurotransmitters A. Today, we know of more than 100 neurotransmitters, and there are many yet to be discovered. B. There are probably more than 1,000 kinds of neurotransmitter receptors. 1. There are subtypes of receptor sites for brain chemicals. 2. The search for and identification of these receptor sites has become one of the hottest areas of brain research. C. There are many neurotransmitters, including: 1. Acetylcholine (ACh) is found throughout the nervous system, where it acts as either an excitatory or inhibitory neurotransmitter, both within the brain and between neurons and muscle cells. 2. Norepinephrine is involved in activation, vigilance, and mood regulation.
3 3. Dopamine has been associated with the thought and mood disturbances of some psychological disorders, and impairment of movement. 4. Serotonin is related to various behaviors such as the sleep/wake cycle, and plays a role in depression and aggression. 5. Endorphins are natural pain suppressors. 6. Glutamate, the most abundant excitatory neurotransmitter, is involved in learning, memory, and pain perception as well as several diseases. D. Any neuron can have hundreds or thousands of axon terminals and synapses, and has the potential for exciting or inhibiting many other neurons. VII. The Human Nervous Systems: The Big Picture A. The central nervous system (CNS) includes all neurons and supporting cells in the spinal cord and brain. B. The peripheral nervous system (PNS) consists of all neurons not found in the brain and spinal cord but in the periphery of the body. C. The PNS is divided into two parts. 1. The somatic nervous system (SNS) includes sensory and motor neurons outside the CNS that serve the sense receptors and the skeletal muscles. 2. The autonomic nervous system (ANS) involves neurons in the peripheral nervous system that activate smooth muscles, such as the stomach, intestines, and glands. a. The ANS consists of the sympathetic and the parasympathetic divisions. b. The sympathetic division is active when we are in states of emotional excitement or under stress. c. The parasympathetic division is active when we are relaxed. VIII. The endocrine system is a network of glands that affects behaviors through the secretion of chemicals called hormones. A. Its function is to transmit information from one part of the body to another. B. Hormones can exert a direct influence over behavior. C. There are several endocrine glands throughout our bodies. 1. The pituitary gland, nestled under the brain, is the master gland, and secretes many different hormones. a. This gland controls such processes as body growth rate, water retention, and the release of milk from the mammary glands. b. It also regulates the output of the thyroid and adrenal glands, as well as the sex glands. 2. The thyroid gland releases thyroxine, the hormone that regulates the pace of the body s functioning. 3. The adrenal glands, located on the kidneys, release adrenaline, or epinephrine, into the bloodstream to activate the body in times of stress or danger.
4 IX. Genetics and Psychological Traits A. The passing of genetic information takes place at conception when the father s sperm unites with the mother s ovum. 1. We inherit chromosomes, genes, and DNA. 2. These, in turn produce certain chemicals, largely proteins and enzymes. 3. We do not inherit talents or psychological characteristics. B. Behavior genetics is the name of the discipline that studies the effects of genetics on psychological functioning. 1. Over several generations, inbreeding studies can indicate which traits tend to run in families. 2. Family history studies were begun in earnest by Francis Galton in the 1800s. 3. The Human Genome Project has cataloged the location of all human genes and seeks to read the information contained on all strands of DNA a. Genes have been found that are related to several outcomes, including Alzheimer s dementia, schizophrenia, alcoholism, and muscular dystrophy. b. It still remains the case that genes carry potentials and the expression of those genes requires an interaction with the environment. 4. Epigenetics refers to a complex biochemical system that exists above the basic level of one s inherited DNA code (genetics) that can affect the actual, overt expression of genetically-influenced traits. X. The Structure of the Spinal Cord A. The spinal cord is a mass of interconnected neurons within the spinal column that transmits impulses to and from the brain and is involved in spinal reflex behaviors; it reaches from the lower back to high in the neck, just below the brain. B. Sensory neurons carry impulses from the sense receptors to the central nervous system. C. Motor neurons carry impulses away from the central nervous system to muscles and glands. D. Interneurons are neurons within the CNS. XI. The Functions of the Spinal Cord A. The communication function of the spinal cord involves the transmission of information to and from the brain. B. The second function of the spinal cord involves the control of spinal reflexes. 1. Spinal reflexes are simple, involuntary responses to a stimulus that involve sensory neurons, the spinal cord, and motor neurons. 2. With a simple spinal reflex, impulses travel in on sensory neurons, within on interneurons, and out on motor neurons. 3. Some spinal reflexes require only sensory neurons, motor neurons, and synapses connecting, and do not require interneurons within the spinal cord itself.
5 XII. The Lower Brain Centers A. The lower brain centers are physically located beneath the cerebral cortex. B. The lower brain centers develop first, both in an evolutionary sense and within the developing brain. C. The brainstem is the lowest part of the brain, just about the spinal cord, and consists of the medulla and the pons. 1. The medulla is the structure in the brain stem that contains centers that monitor reflex functions such as heart rate and respiration. a. Cross laterality is the arrangement of nerve fibers crossing from the left side of the body to the right side of the brain, and from the right side of the body to the left side of the brain. b. Cross laterality begins in the medulla and also occurs in the pons. 2. The pons is a brain stem structure that forms a bridge that organizes fibers from the spinal cord to the brain and vice versa. D. The cerebellum is a spherical structure at the rear, base of the brain that coordinates fine and rapid muscular movements. 1. Damage to the outer region of the cerebellum results in intention tremors, which are involuntary trembling movements. 2. Damage to inner areas of the cerebellum results in tremors at rest. E. The reticular formation is a network of nerve fibers extending from the base of the brain to the cerebrum; it controls one s level of activation of arousal. F. The basal ganglia are collections of structures in the center of the brain that are involved in the control of large, slow movements; a source of much of the brain s dopamine. 1. Dopamine, created and usually found in great quantity in the basal ganglia, is insufficient in those persons with Parkinson s disease. 2. L-dopa is a drug that increases dopamine availability in the basal ganglia. 3. Transplanting stem cells from aborted human fetuses (and other sources) into the brains of persons with Parkinson s may reverse the course of the disease. G. The limbic system is a collection of structures near the middle of the brain involved in emotionality and long-term memory storage. 1. The amygdala produces reactions of rage or aggression (and some other emotions as well) when stimulated. The amygdale has recently been implicated in our ability to experience fear and to recognize fear in others. 2. The septum reduces the intensity of emotional responses. 3. The hippocampus is involved with the formation of memories for experiences. a. More recent memories of life events are more disrupted by damage to the hippocampus than are older memories. b. The hippocampus also plays a role in memories that involve the experience of fear. 4. The hypothalamus is a structure made up of several nuclei involved in feeding, drinking, temperature regulation, sex, and aggression. H. The thalamus is located just below the cerebral cortex; it projects sensory impulses to the appropriate areas of the cerebral cortex. 1. While it also acts like a relay station, its major function involves the processing of information from the senses.
6 2. Like the pons, nuclei in the thalamus may have a role in establishing normal patterns of sleep and wakefulness. XIII. The Cerebral Cortex A. The cerebral cortex is the large, convoluted outer covering of the brain that is the seat of voluntary action and cognitive functioning. B. Neuroscientists have learned about the structures and functions of the cerebral cortex by using several different methods. 1. One can work backward, examining damaged areas of the brain and discovering what function or functions have been lost as a result. 2. Surgical lesions (cuts) or ablations (removals) can be made to see what happens to behaviors and mental processes without the brain tissue affected, 3. Small electrodes can be inserted into the brain tissue of conscious persons to stimulate small areas of the brain to see the result. 4. The electroencephalogram (EEG) can measure the electrical activity of brain functioning, a. The procedure is not invasive. b. It provides only general information. 5. Areas of the intact, functioning brain can be studied by several imaging techniques. a. The CAT Scan (or CT scan) or computerized axial tomography image is a series of thousands of X-ray images of slices of the brain. b. The PET scan (positron emission tomography) shows the functioning brain by looking at minute radioactive traces that are brightest in areas of brain activity. c. Magnetic resonance imaging (MRI) or functional magnetic resonance imaging (fmri) measures the movement of molecules of blood, providing clear images of brain activity, even in very small areas. XIV. Lobes and Localization A. A crevice runs down the middle of the cortex dividing it into the left and right cerebral hemispheres. B. There are four major divisions of each hemisphere, called lobes. 1. The frontal lobes (left and right) are largest, and are defined by two crevices called the central fissure and the lateral fissure. 2. The temporal lobes are located at the temples, below the lateral fissure, with one on each side of the brain. 3. The occipital lobes are at the back of the brain. 4. The parietal lobes are wedged in behind the frontal lobes and above the occipital and temporal lobes. C. In terms of function, there are three major areas of the cerebral cortex. 1. Sensory areas receive and process impulses from sense receptors. 2. Motor areas are where most voluntary muscular movements originate. 3. Association areas are in the frontal, temporal, and parietal lobes where incoming sensory input is integrated with motor responses, and where higher mental processes are thought to occur.
7 a. Broca s area controls the production of speech. b. Wernicke s area is involved in speech comprehension and organizing ideas. c. Planning ahead and forethought in general seem to be localized in the very front of the frontal lobes. XV. The Two Cerebral Hemispheres: Splitting the Brain A. The two hemispheres are connected by the corpus callosum, a network of fibers. B. The split-brain procedure involves surgical lesioning (or removal) of the corpus callosum, the structure that separates the functions of the left and right hemispheres of the cerebral cortex and is a treatment of last resort for epilepsy. C. Virtually no behavior or mental process is the product of one hemisphere alone, but one hemisphere may be dominant with respect to a given task or processing certain types of information, the left hemisphere usually associated with linguistic and serial processing while the right hemisphere is associated with visual/spatial processing and seems more involved in emotionality. XVI. SPOTLIGHT: The Two Sexes: Male and Female Brains A. Except for differences that are directly related to reproductive function, there are very few differences that are of real consequence between male and female brains. Nonetheless, some research suggests that there is more activity in the limbic system (associated with emotional reactions, rewards and addictions) in males than in females while they are playing video games! B. There is a difference in the lateralization of the brains of left-handed persons compared to right-handed persons, but no differences in cognitive abilities. 1. Similar findings for male/female differences have proven difficult to replicate. 2. Women are more likely than men to show signs of recovery from a stroke because the unaffected side of the brain is better able to compensate for losses in the affected side.
8 LEARNING OBJECTIVES 1. Describe the main structural features of a neuron. 2. Explain the function of each structure. 3. Describe myelin and explain the functions it serves in the central nervous system. 4. Explain neurogenesis and discuss its significance. 5. Discuss the basic process involved when a neuron fires, describing the involvement of resting and action potentials. 6. Explain the concept of neural threshold and the all-or-none effect. 7. Describe how neural impulses are transmitted at the synapse. 8. Name five neurotransmitters and indicate a psychological process in which each is involved. 9. Name the divisions of the human nervous system and indicate how they relate to one another. 10. Describe the function of the endocrine system and the roles of the pituitary, thyroid and adrenal glands. 11. Discuss the ways in which researchers have been studying the effects of genes on psychological functioning. 12. Define sensory neurons, motor neurons, and interneurons. 13. Describe the basic structure and two major functions of the spinal cord. 14. Discuss the two brain stem structures, their location, and their functions. 15. Explain cross laterality. 16. Describe the cerebellum and reticular formation, their locations, and their major functions. 17. List the location and major functions of the RAS, limbic system, thalamus, septum, amygdala, and hippocampus. 18. Discuss the role the basal ganglia plays in Parkinson's disease.
9 19. Describe some of the techniques that have been used to study the structures and functions of the brain. 20. Describe the location and function of the four lobes of the cerebral cortex. 21. Identify and summarize the functions of the sensory, motor, and association areas of the cerebrum. 22. Briefly summarize the respective functions of the right and left hemispheres. 23. Explain the split-brain procedure, and describe how split-brain operations facilitate the study of brain functions. 24. Discuss whether there are any significant differences between the brains of females and males.
10 Key Terms and Concepts neuroscientists neuron cell body dendrites axon myelin axon terminals neurogenesis neural impulse chemical ions resting potential action potential refractory period
11 all-or-none principle neural threshold synapse synaptic cleft vesicles neurotransmitters receptor sites excitatory inhibitory reuptake central nervous system (CNS) peripheral nervous system (PNS) somatic nervous system autonomic nervous system sympathetic division
13 pons cerebellum reticular formation basal ganglia Parkinson s disease limbic system hypothalamus thalamus cerebral cortex electroencephalogram (EEG) sensory areas motor areas association areas corpus callosum split-brain procedure
14 A Few Flash Card Possibilities for Chapter 2 (Remember: The best flash cards are those you make yourself.) PARTS of a NEURON cell body (& cell s nucleus), dendrites, and axon with bare endings MYELIN white, fatty covering on some axons; insulates, protects, speeds impulses CHEMICAL ION electrically charged (+ or -) chemical particle NEURAL THRESHOLD minimum amount of stimulation required to get a neuron to fire COMPONENTS of the ANS autonomic nervous system = sympathetic + parasympathetic divisions ENDOCRINE SYSTEM glands that release hormones into the bloodstream (slower than nervous system) SYNAPTIC SPACE tiny space between the axon of one neuron and dendrite of the next where neurotransmitters go FUNCTIONS of SPINAL 1. spinal reflex behaviors CORD 2. speed impulses to and from brain PARTS of BRAIN STEM the medulla and the pons PARTS OF LIMBIC SYSTEM 1. amydala (emotion) 2. septum (emotion) 3. hippocampus (memory) CORPUS CALLOSUM fibers that connect left and right hemispheres of cerebral cortex severed in split brain operation CEREBRAL CORTEX LOBES frontal, temporal, occipital, & parietal
15 Practice Test Questions Multiple Choice 1. Which of the following lists the major structures of the neuron in the correct order? a. cell body, dendrite, axon b. axon, dendrite, cell body c. dendrite, cell body, axon d. Any of these may be correct, depending upon the particular neuron involved. 2. Of the following structures, which is likely to occur in neurons in the greatest number? a. dendrites c. axons b. nuclei d. cell bodies 3. Myelin sheaths serve several different functions. Which of these is NOT something that myelin normally does? a. insulates axons from other nearby axons b. helps to speed up impulse transmission c. produces and stores the neuron s neurotransmitters d. protects the delicate axon against physical damage 4. When a neuron is at rest, a. it has no electrical charge. b. the inside of the neuron has a negative charge compared to the outside. c. it is in the process of firing, or transmitting an impulse. d. chemical ions are racing in and out of the neuron. 5. When an impulse moves down or along a neuron, what physically moves from one end of the neuron to the other? a. the chemical ions involved c. the fluids within the neuron b. the neural membrane itself d. nothing 6. The all-or-none principle states that a. a neuron will either fire or it won t. b. neural impulses always travel in one direction. c. some neurons always fire; some neurons never fire. d. neurons either have a threshold or they don t. 7. Although there are many specific neurotransmitters, we can classify them in terms of their actions as being either a. central or peripheral. c. excitatory or inhibitory. b. sensory or motor. d. axonic or dendritic.
16 8. The action of neurotransmitters at the synapse is basically a(n) process. a. electrical c. chemical b. mechanical d. psychological 9. Of these, which neurotransmitter is said to act like a natural pain suppressant, influencing our experience of pain? a. serotonin c. acetylcholine b. endorphin d. dopamine 10. The first major division of the human nervous system is into the nervous system and the nervous system. a. motor; sensory c. central; peripheral b. affective; cognitive d. somatic; automatic 11. Of the following, which nervous system is most intimately involved in our experience of emotion? a. peripheral nervous system c. automatic nervous system b. parasympathetic nervous system d. sympathetic nervous system 12. The endocrine system operates mostly on the basis of a. neurons in the spinal cord. c. neurotransmitters in the brain. b. hormones in the bloodstream. d. ions in the neuron. 13. The endocrine gland most intimately involved in metabolism (the body s rate of oxygen use, and growth) is the gland. a. pituitary c. thyroid b. execrine d. adrenal 14. The Human Genome Project is reinforcing the notion that a. every behavior can be accounted for by the action of a few genes working together. b. scientists are unlikely to ever understand the relationship between individual genes and human behaviors. c. the in heritance of proteins and enzymes at conception accounts for the individual s assortment of genes and chromosomes. d. any traits involving behavior are likely to have a complex genetic basis. 15. Conscious, voluntary actions originate in the a. cerebral cortex. c. brain stem. b. spinal cord. d. muscles and glands.
17 16. When we look at a cross-section of the spinal cord, we clearly see areas that are made up of white matter. In this white matter we have a. the area where reflex action takes place. b. fibers going to and from the brain. c. nerve fibers entering and leaving the spinal cord itself. d. the part of the CNS that controls emotions. 17. In a spinal reflex, neural impulses enter the spinal cord on a. motor neurons. c. sensory neurons. c. ascending tracts or fibers. d. descending tracts or fibers. 18. As one travels up through the brain from the spinal cord, the first brain structure to be encountered would be the a. corpus callosum. c. medulla. b. basal ganglia. d. thalamus. 19. Which of the following is best associated with the medulla? a. thinking or problem solving b. breathing reflexes c. sensory projections to the cerebral cortex d. muscle coordination 20. Cross laterality occurs (mostly) in the a. spinal cord. b. brain stem. c. limbic system. d. basal ganglia. 21. If I were to electrically stimulate the reticular formation of a sleeping cat, the result would be that the cat would a. no longer demonstrate normal emotional responses. b. die. c. begin to make small twitching motions, indicative of dreaming. d. wake up. 22. Which lower brain center is most clearly involved in the experience of being thirsty? a. the hypothalamus c. the amygdala c. the hippocampus d. the septum 23. The brain structure that sends, or projects, sensory impulses to the appropriate area of the cerebral cortex is the a. thalamus. c. basal ganglia. b. projectorator. d. body sense area of the parietal lobe. 24. The small structure in the limbic system that seems to be involved in the formation of longterm memories is the a. amygdala. c. ganglion. b. hippocampus. d. septum.
18 25. Of these, the neuroimaging technique that involved the injection of a radioactive tracer element is the a. EEG. c. CT, or CAT scan. b. PET scan d. MRI or fmri. 26. Our body senses (touch, pressure, and the like) are largely processed at the front of the lobe of the cerebral cortex. a. occipital c. temporal b. parietal d. frontal 27. The two hemispheres of the cerebral cortex are richly interconnected by the a. white matter of the spinal cord. c. corpus callosum. c. frontal lobe. d. left and right ventricles. 28. A person who has had a split-brain operation is blindfolded. A paper clip is placed in her LEFT hand and we ask her to tell us what we have placed there. She is most likely to a. tell us that the object is a paper clip and be able to point to it when it is placed on a table with other objects. b. have no idea of what is in her hand. c be unable to tell us what we put in her hand, but be able to point to the paper clip when it is on a table with other objects. d. respond just as if we had placed the paper clip in her RIGHT hand. 29. The difference between male and female brains for which there is the greatest amount of evidence is that a. the brains of females are significantly larger than those of males. b. female brains have no hypothalamus. c. the brains of females are more likely to recover from traumas, such as a stroke. d. men tend to use their frontal lobes for the storage of long-term memories, whereas women use their parietal lobes. True/False 1. True False Myelinated neurons carry impulses faster than do unmyelinated neurons. 2. True False The number of neurons in your body gradually increases from birth until they begin to die off in old age. 3. True False Every neuron has its own threshold the minimal amount of stimulation required to get it to fire. 4. True False Neurotransmitters move across a synapse to either excite a new impulse in the next neuron or to inhibit that neuron from firing.
19 5. True False Because it uses the bloodstream instead of the neurons, information travels faster in the endocrine system than it does in the nervous system. 6. True False The correct sequence of impulses involved in a spinal reflex may be summarized as: in on sensory neurons, within on interneurons, and out on motor neurons. 7. True False The basal ganglia are involved in the movement of large skeletal muscles, such as those that are involved in walking. 8. True False Visual information is processed in the occipital lobe of the cerebral cortex. 9. True False Someone whose corpus callosum has been severed in a split-brain operation will probably need to be hospitalized or closely supervised for the rest of his or her life. 10. True False There are simply no structural differences in general between the brains of men and the brains of women.
20 Answers to Practice Test Questions Multiple Choice 1. c Within a neuron, impulses travel (typically) from dendrite to cell body to axon. Here s a good example of an item for which all of the above is not the correct choice. 2. a A neuron will have only one cell body and one nucleus. As it happens, some may have two axons, but the structure most likely to occur in great numbers is the dendrite. 3. c Myelin serves each of the functions named in alternatives a, b, and d. Be careful to note the not in this item. Neurotransmitters are manufactured within the neuron and stored in vesicles. 4. b At rest, a neuron is in position to fire, with many more negative ions inside and positive ions outside, which makes the second alternative correct. 5. d Nothing physically moves down a neuron when it fires. Physical movement is of ions going in and out of the neuron. What moves down a neuron is where this ion movement takes place. 6. a This one is straightforward. Alternative a is correct by definition. 7. c Watch out for this item! An important phrase in this item is in terms of their actions, which means we re looking for what they do which is to either excite or inhibit neural impulse transmission. 8. c Within a neuron, impulse transmission is electrochemical, but at the synapse, given the action of the neurotransmitters, it is basically a chemical process. 9. b Actually, there are several different endorphins, but each is involved in moderating our experience of pain. 10. c The major division of the human nervous system is into central and peripheral systems. Each of these, in turn, has its own divisions. 11. d It is important to know how the various nervous systems are interrelated, and the major functions of each. While the parasympathetic division is active when we are relaxed and calm, the sympathetic division is involved in emotionality. Note the spelling of alternative c; there is no such thing as an automatic nervous system. 12. b The endocrine system influences behaviors and mental processes, but does so through hormones transmitted through the bloodstream. 13. c The thyroid gland secretes thyroxin the growth hormone and is, thus, the best choice here. Yes, the pituitary does influence this gland, as it influences them all, but this item is more specific than that. 14. d. In mapping all of the human genes and chromosomes, the Human Genome Project has reached a significant goal. It remains the case, however, that the influence of genes o behavior is incredibly complex, almost certainly involves the interaction of several genes and the interaction of those genes with forces in the environment. 15. a Conscious, voluntary actions originate in the cerebral cortex, even though other CNS structures may be involved. 16. b The white matter looks white because of the myelin that surrounds the axons of the fibers going up and down the spinal cord, to and from the brain. 17. c This is a straightforward terminology item. For the spinal reflex we have: in on sensory neurons, within on interneurons, and out to muscles or glands on motor neurons.
21 18. c Although it is difficult to tell exactly where the spinal cord leaves off and the brain begins, the first brain structure to be encountered would be the medulla. 19. b The medulla contains centers (nuclei) that control several important reflexes, including respiration, or breathing. 20. b Cross laterality occurs in the medulla and in the pons. Because these two structures make up the brain stem, this is the best answer. 21. d The reticular activating system, as the name implies, controls levels of arousal. All that would happen in this scenario is that the cat would wake up. 22. a The hypothalamus is not only involved in the thirst drive, but it is also implicated in the hunger drive, temperature regulation drive, sex drive, and others. 23. a This item describes very succinctly the function of the thalamus. 24. b Although the septum and the amygdala are considered to be parts of the limbic system, there is no evidence that they have anything to do with memory directly. The structure that does is the hippocampus. 25. b The CT and MRI techniques do not really require an injection of any sort, and the EEG measures electrical activity and is not really an imaging technique in the first place. 26. b This gets a bit technical. But you should know the major features of cerebral localization (vision, hearing, movement, etc.), and you should know that the body senses are processed in the front of the parietal lobe. 27. c It is the corpus callosum that normally interconnects the two hemispheres of the cerebral cortex so that as soon as one side knows what is going on, the other side knows as well. 28. c Don t panic just because this item is wordy. Remember the basics of the split-brain procedure, and remember that speech is a left-hemisphere activity, and that information from the left hand would be processed in the right hemisphere. These details make alternative c the correct one. 29. c As a rule of thumb, there are very few differences between the brains of females and males either structurally or functionally. For reasons not yet fully understood, however, the brains of females do recover more quickly from cerebral accidents or traumas, such as strokes. True/False 1. T Indeed, one of the important functions of myelin is to speed impulses along. 2. F This may sound logical, but it is not true. We are born with more neurons than we ll ever have again. 3. T The threshold of one neuron may be different from that of other neurons, but every neuron does have its own threshold value of stimulation required to get it to fire. 4. T This is a simple, but accurate, statement of what neurotransmitters do. 5. F Actually, because it uses the bloodstream rather than neurons, the action of the endocrine system is significantly slower than the action of the central nervous system. 6. T This is basically a repeat of item #16 in true-false form. This sequence is correct. 7. T This statement is true, reinforcing the notion that the basal ganglia are implicated in Parkinson s disease. 8. T Again, you should know the localization of the major functions of the cerebral cortex, including the fact that vision is processed in the occipital lobe.
22 9. F No, as it happens, it is often very difficult to tell if someone has had this procedure, except when certain brain functions are tested in the laboratory. Split-brain patients can, and do, lead relatively normal lives. 10. F Granted, as I said above, there are very few differences between the brains of females and males, but to claim that there are NO structural differences is silly.
23 Experiencing Psychology How Fast Do Neural Impulses Travel? As neural impulses speed from one part of your body to another, they travel at incredibly high rates of speed. You step on a tack, and the experience of pain is nearly immediate. Can you measure the speed of impulse transmission without the use of sophisticated equipment? Yes, you can, with the help of a few friends, if you don t mind being a little imprecise. Ask ten people to stand next to each other with their eyes closed and holding hands. At your signal, the first person is to squeeze the hand of the next person who will, in turn, squeeze the hand of the next person, and so on, until the last person s hand is squeezed and signals so by raising his or her free hand. As you give the signal to begin, you start a stopwatch and stop it when that last person signals that he or she has received a squeeze. Repeat the procedure until the time becomes reasonably stable. Divide that time by 10. Now have the people in the same group put their left hands on the right shoulders of the person standing next to them. At your signal, the first person squeezes the shoulder of whomever is standing to the left. The second person then squeezes the should of the person to his or her left and so on, until the last person signals being squeezed. Again, repeat the procedure until the time interval stabilizes, and again divide by 10. Although it is a crude measure, the difference between the two time intervals, once each has been divided by 10, represents the time it takes for the neural impulses to travel between the hands and the shoulders of your volunteers. If you get an average of the length of their arms, you could convert your measurements into inches per second. [This project is adapted from: Rozin, P. & Jonides, J. (1977). Mass reaction time: Measurement of the speed of the nerve impulse and the duration of mental processes in class. Teaching of Psychology, 4, ]
24 Psychology on the Internet 1. NEURONS: THE BUILDING BLOCK OF THE NERVOUS SYSTEM When one considers the complexity of the simple nerve cell, it is no wonder that a full understanding of how the human brain functions remains beyond the grasp of contemporary science. After all, there may be 100 billion neurons in the human brain. And as we learn in Chapter Two, although the neuron is but a single cell, it is in no way to be considered simple. As you might imagine, many of the Internet websites that can help us appreciate the neuron are from disciplines other than psychology. Many such websites are simply beyond the level of a beginning psychology class. I have tried to choose a few that are instructive, not overwhelming. Indeed, I have included a few specifically designed for kids and one designed for beginning neuroscientists. All of them involve colorful illustrations, simple explanations, and even an occasional animation. (a website called Neuroscience for Kids, maintained by Eric H. Chudler, PhD, of the University of Washington in Seattle.) 2. FROM ONE NEURON TO ANOTHER: THE SYNAPSE The sites listed above focus largely on the structures of neurons and, in general terms, how they function. The activity of just one neuron is exciting enough, but nothing much really happens in the nervous system unless neurons can communicate with each other. That communication takes place at the synapse, and the process is most dynamic indeed. The following websites deal with synaptic activity and the neurotransmitters that make it all happen. (More of Neuroscience for Kids with links to others, including a summary from the Society of Neuroscience, How do nerve cells communicate? )
25 (Neuroscience for Kids covers neurotransmitters) 3. THE ENDOCRINE SYSTEM The endocrine system mirrors the nervous system in many ways. Here are two websites that expand that discussion. (If you have a question about the endocrine system or hormones, you can find it answered here a service of the U.S. National Library of Medicine and the U.S. National Institutes of Health.) (website of the most active professional organization of endocrinologists in the world ) 4. THE SPINAL CORD Almost all of the websites in any way related to the spinal cord have a focus on spinal cord injuries and their treatment. We can do no better here than to recommend the same two sites we mentioned in the text. (You will find out a lot about the late actor Christopher Reeve, and discover a lot about research and treatment programs for people with spinal cord injuries.) (Under the button News and Information a click takes you to a very long list of Resources on the spinal cord, and up-to-date Fact Sheets. )
26 5. THE LOWER BRAIN CENTERS AND THE CEREBRAL CORTEX I suspect that you have a pretty good idea of the extent of the coverage of the brain on the Internet. In less than 0.20 seconds, Google located 20,700,000+ entries! There probably are very good sites buried in the list. For introductory psychology students I would caution that we not get carried away. Chapter Two provides a comprehensive summary of what you need to know for now. Nonetheless, there are a few sites that are worth a visit. (One of many with a focus on brain injury, this site provides some very nice and colorful visuals) (A website derived form the PBS series on the brain. You will find excellent visuals, of the brains of babies, children, teenagers, adults, and the elderly.) (The human brain is a rather homely organ. This site (from Michigan State University) provides photographs of actual MRI sections of the brain. It is not very pretty, and not very instructive, but if you d like to see what a brain really looks like, here is a place to go. (this website gives an opportunity to explore what the brain looks like. Click on Brain Atlas and you will find great images that are easy to navigate.) (site of the Society for Neuroscience, 34,000 thousand scientists worldwide devoted to the study of the brain. I recommend clicking on Publications. The first three on the list are technical, scientific journals and pretty heavy reading. Brain Briefings will reward you with a list of scores of 2-page summaries on how neuroscience discoveries lead to clinical applications. Perhaps the most useful part of this section of the site is Brain Facts a 52-page primer in pdf format.)
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